Investigating the Arenyl-Diene Double [3 + 2] Photocycloaddition Reaction

The double [3 + 2] photocycloaddition reaction involving arenyl−dienes has been used to assemble seven separate [5.5.5.5] fenestrane structures that include ether and aza variants. The primary photolysis step was a <i>meta</i> photocycloaddition reaction, while a secondary photocycloaddition step formed the fenestrane structure. Investigations involving the insertion of an additional methylene group into the basic arenyl−diene skeleton failed to afford the desired [5.5.5.6] fenestrane structure. The presence of an oxime moiety in the aromatic photosubstrate allowed the primary photolysis step to take place; however, an attempted secondary photocycloaddition reaction involving the oxime did not provide the intended polyheterocyclic fenestrane. An alternative strategy to form various “criss-cross” double <i>meta</i> photocycloadducts was investigated and led to the discovery of a Paterno−Büchi cycloaddition reaction between acetone and an angular <i>meta</i> photocycloadduct. Other novel thermally and photochemically mediated skeletal rearrangement reactions were also recorded.